The main character, who is also a Master in the Holy Grail War, is interesting as well. He has to navigate through the dangerous and complex world of the Grail War, dealing with the powerful Servants and other Masters. His growth throughout the story, from being a relatively inexperienced person to someone who can hold his own in this cut - throat world, is a great aspect of his character.
I think Mordred is quite interesting. She is King Arthur's 'son' and has a complex relationship with her 'father'. Her rebellious nature and strong combat abilities make her stand out. Another interesting one is Jeanne d'Arc. She plays a crucial role in the story, trying to bring some sort of balance between the warring factions.
Kiritsugu Emiya is quite interesting. His cold - blooded yet ultimately well - intentioned approach to the Grail War sets him apart. He's willing to do whatever it takes to win, even if it means using morally ambiguous tactics. Another is Gilgamesh. His arrogance as an ancient king and his overpowering abilities make him a captivating character. And then there's Saber, with her sense of honor and the internal conflict she has between her past as a king and her current role as a Servant.
One of the main themes is the concept of heroism. It explores how different characters, especially the summoned heroes, embody the ideals of heroism in a complex and often dangerous world. Another theme is fate itself. The characters seem to be guided by some pre - ordained fate, yet they also struggle against it, trying to make their own choices within the framework of the Holy Grail War.
Saber is one of the most interesting characters. Her complex backstory as King Arthur, a female in a male - dominated role, and her struggle with her ideals of kingship make her stand out. Another interesting character is Gilgamesh. His extreme arrogance and his view of himself as the ultimate being are fascinating. He also has a deep understanding of power and the nature of the Grail War.
Astolfo is also quite fascinating. With his flamboyant personality and unique set of abilities, he stands out. He often brings a sense of unpredictability to the story. His loyalty to his side but also his ability to befriend those on the other side make him a complex and engaging character. There's also Jeanne, whose role as a Ruler and her struggle to maintain balance in the war is really interesting.
Saber is really interesting. She's a strong and noble Servant with a complex past. Her code of honor and her struggle to reconcile it with her present situation make her stand out. Another interesting character is Archer. His cynical view and his connection to Shirou add a lot of mystery and depth to the story.
I think Kiritsugu Emiya is really interesting. His methods are often extreme as he's willing to do whatever it takes to achieve his goal of world peace, even if it means sacrificing the few for the many. He has a complex past that shapes his actions in the Holy Grail War.
Archer is one of the most interesting characters. His complex backstory, being a future version of Shirou, gives him a unique perspective. He is jaded by his experiences yet still holds a certain sense of purpose.
Gilgamesh is another highly popular character. He has a very arrogant yet charismatic personality. His vast power and his role as one of the oldest and most powerful Servants in the series draw a lot of attention. Additionally, Rin Tohsaka is popular. She is a smart and capable mage who plays an important role in the story.
There could be a mysterious character in the novel who seems to have some knowledge or power related to the dark side of fate. Their actions and motives would be quite intriguing as they might be manipulating or guiding the events in some way.